EM Microelectronic RFID ICs

EM Microelectronic RFID ICs: EM4325, EM4423, and Specialty ICs

EM Microelectronic (EM Micro) is the semiconductor division of The Swatch Group and one of the oldest RFID IC designers. While less prominent in commodity retail than Impinj or NXP, EM Micro holds strong positions in specific verticals: active-assisted RFID, sensor-integrated tags, dual-frequency tags, and coupling RFID standard." data-category="Standards & Protocols">ISO 15693 HF. This guide covers the ICs most relevant to system designers.

EM Micro Product Philosophy

EM Micro specialises in ultra-low-power analog design. Their ICs tend to have slightly lower production volumes than mass-market players but offer features not available elsewhere: integrated temperature sensors, battery-assist circuits, and multi-protocol support. They are the IC vendor of choice when a project requires something beyond a standard passive EPC Gen 2 chip.

EM4325: Battery-Assisted UHF with Sensor Interface

The EM4325 is a semi-passive tag IC combining EPC Gen 2v2 / EPC Gen2 UHF standard." data-category="Standards & Protocols">ISO 18000-63 UHF RFID with a battery-assist circuit and an analog sensor interface. It is the primary IC for cold-chain and pharmaceutical temperature monitoring.

The 2 KB user memory differentiates EM4325 from nearly all commodity UHF ICs — it stores a full temperature log on-tag, readable without network connectivity. This is critical for cold-chain break detection at receiving: a simple handheld scan shows the entire transit temperature history without querying a server.

Application pattern for cold chain:

1. Tag programmed at origin with SGTIN and baseline temperature thresholds
2. Battery activates the EM4325 sensor circuit; temperature samples logged every N minutes
3. At destination, any RAIN RFID reader inventories the EPC and reads the temperature log from user memory
4. Middleware compares log against permitted thresholds and flags exceptions

For guidance on encoding user memory correctly, use the Memory Planner and see Tag Memory Planning.

EM4423: Dual-Frequency HF + UHF

The EM4423 is a dual-interface IC supporting both ISO 15693 (HF 13.56 MHz) and EPC Gen 2v2 (UHF 860–960 MHz) simultaneously. A single tag can be read by either a UHF supply-chain reader or an HF near-field reader without any switching.

Why dual-frequency?

Retail and logistics use UHF for bulk scanning. Consumer-facing verification (brand authentication, recycling scan, NFC-aware smartphone) uses HF. A product tagged with EM4423 serves both channels with a single inlay, avoiding double-tagging costs and the data synchronisation complexity of maintaining two serial numbers per item.

Dual-frequency inlays require antenna designs that operate efficiently at both 13.56 MHz and 860–960 MHz on the same substrate — a non-trivial RF engineering challenge. Commercial dual-frequency inlays from Smartrac (Track) and Tatwah are available based on EM4423.

EM4100 / EM4200: LF Legacy ICs

EM Micro's LF product line (125 kHz, read-only) includes:

EM4100 is the single most widely deployed LF RFID chip globally, found in hundreds of millions of access-control key fobs and cards. Its protocol is publicly documented and has been cloned extensively, making it inappropriate for any application requiring security. See RFID Security Threats for context on LF vulnerabilities.

EM4750 / EM4750A: ISO 15693 HF ICs

For ISO 15693 deployments — library RFID, industrial asset tracking, anti-counterfeiting labels — EM Micro offers:

The EM4750A is notable for adding AES-128 mutual authentication to an ISO 15693 tag — a combination not available from most vendors. It is used in industrial calibration labels where the tag must prove its authenticity to a proprietary reader.

IC Selection by Vertical

Integration Notes

EM Micro does not sell finished tags or readers — only ICs. When designing with EM4325 or EM4423, work with an inlay manufacturer who has an established design-in relationship with EM Micro for antenna co-design. The battery-assist circuit of the EM4325 requires careful PCB or flex-circuit layout to avoid self-oscillation.

For cold-chain tag selection, compare with the Harsh Environment Tags guide for environmental ratings.

See also: Impinj Generations Compared, NXP UCODE Guide, Passive vs Active RFID Tags.